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  1. #1
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    917

    Carel spkt00b6r0 pressure transducer

    I have a unit with this pressure transducer that is being used to directly control a drive that controls condenser fans. The spec sheet states 4.5 to 5.5 VDC supply. My question is that the equipment manufacturer has this being powered from the drives 10 VDC output. I believe this an issue since it is getting supplied by 2x its stated supply voltage. Any thoughts on this?


    http://catalog.carelusa.com/item/pre...rs/spkt00b6r0#

  2. #2
    Join Date
    Dec 2007
    Location
    Connecticut
    Posts
    890
    Based on the cut sheet, I think you're right. Are you having issues with the unit? If so, I would get a 5vdc power supply and rewire it. Did you verify that the transducer is actually getting 10vdc and not the range required? They could have limited the 10vdc output to a different range with internal drive parameters.

  3. #3
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    917
    It is in an Innovent MUA unit and there has been a lot of issues with this unit from day one from what I hear. It is not one of my regular sites, only visit when its down and other techs are tied up. What brought me there this time was tripping on high pressure. Found that the VFD was only going to 45.3HZ, think it was 7.3VDC input at drive AI1 and discharge pressure over 500 PSI.

    Called one of the normal techs to see if anyone had made parameter changes to the drive recently. Response was no, but drive was just replaced and few weeks ago. He also stated that he has had to clean the condenser coil about every 3 weeks during the summer months. I called the tech that replaced the drive and he said it was replaced because the old one would not start, it had power but couldn't tell me what any of the signal inputs were at that time. He said he changed all parameters to match old drive which I can say there were parameters missed because the book on site is only the basic manual that he marked off parameters in.

    This unit has also had a history of "refrigerant leaks" and starting to make me wonder how long this thing has been running with high discharge pressures and possibly opening the relief valve.

    The transducer is connected directly to the drive, 10VDC supply to transducer from drive 10VDC+. It is a Yasakawa J1000. I changed some parameters and verified control of VFD at what pressure I wanted using a signal generator based off the spec range of .5 - 4.5 VDC and 14 - 677 psi (not thinking about the higher supply voltage) but as stated my supply voltage was higher than spec and now my transducer output appears to be based on a high of 10.2 VDC supply output of drive rather than the 4.5 VDC spec. Which is also on the transducer tag. There is a Carel PCO3 controller in the unit with a 5VDC supply, but with it being almost 100 outside, getting late and this unit is for a lab I just needed to get it running.

    I will have to get in touch with Carel and see what they have to say if this will cause any issues with accuracy or operation of the transducer. If it is I will add a separate DC power supply for the transducer. May just do it anyway.

  4. #4
    Join Date
    Jun 2009
    Location
    StL, MO
    Posts
    581
    Here's a good explanation (if you do the math) of the effect of supply voltage on a ratiometric transducer. http://cgproducts.johnsoncontrols.co...F/12011190.pdf
    Considering the existing transducer has seen higher than spec voltage for a while, I'd change out the transducer with one that can accept the 10V supply.
    UA LU 562

  5. #5
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    917
    Thanks. New transducer will be getting ordered. Just makes me scratch my head why a manufacturer would supply it with the wrong voltage.

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